The relationship between humans and horses has developed over thousands of years. Theearliest record of human use of horses comes from cave paintings in France and Spain fromaround 15000 years ago, when horses were hunted for food and hides (Goodwin, 2002).Archaeological evidence for the domestication of horses dates back to around 6000 yearsago in the Ukraine, Egypt and Western Asia (

Ibid.

).Through breeding and training, horses have been persuaded to assist in diverse fields ofhuman endeavour. Horses have played a major role in human history, from providingdraught power in agriculture and transport to influencing the outcomes of war. Today, theyare valued for their use in recreation, competition and sport, whilst in many parts of the worldthey continue to provide an important source of draught power, meat and milk.Whilst horses are undoubtedly one of the species most highly valued by humans, all toooften the way in which we keep, train and use them can have serious detrimentalconsequences for their welfare. How much do we actually know about their naturalbehaviour and the inner workings of the horse’s mind and how can this knowledge be usedto improve their welfare?

Natural Behaviour

Horses are adapted for life on open grasslands and will range up to 80km per day (Davidsonand Harris, 2002). Horses prefer to graze, although they will also browse on a wide variety ofvegetation (

Ibid.

). Feral and free-ranging horses spend around 16 to 18 hours a day foraging(

Ibid.

), consuming over 50 varieties of forage daily (Goodwin

et al

, 2005).Studies of feral horses indicate that they organise themselves into two different types ofherd: the family or harem band and the bachelor band (Crowell-Davis, 1993; Waran, 1997).The family band typically consists of a single stallion, several mature mares and their foalsand juvenile offspring. In some cases there may be more than one stallion, with thedominant stallion mating more than the subordinate ones. Colts leave, or may be expelled bythe stallion, when they are one to two years old and form bachelor bands, whilst most filliesleave when they are one and a half to two and half years old and join other existing haremsor form new ones with males from bachelor bands (Goodwin, 1999).In the wild, membership of a herd is such an important survival strategy that the socialbehaviour of the horse functions to minimise conflict within the group and so promotes itsstability (Goodwin, 2002). Subordinate individuals avoid moving close to dominant ones andovert aggression is relatively rare (Goodwin, 1999). Thus, dominance relationships orhierarchies result in reduced aggression and increased cohesion of the group (Waran,1997). Once the dominance hierarchy is established, aggression becomes more ritualised,with threats largely replacing actual attacks (Crowell-Davis, 1993). The dominance order isunidirectional between individuals but is not necessarily always linear so that horse ‘A’ maybe dominant over horse ‘B’ who may be dominant over horse ‘C’, but horse ‘C’ may bedominant over horse ‘A’ (Houpt

et al

, 1978).A central mechanism of herd cohesion is the formation of pair bonds and mare-foal bonds.Within the herd, individuals have preferred associates with whom they spend most of theirtime and these are usually horses of similar social rank (Kimura, 1998). Within peer groups,

close pair bonds develop between individuals and can persist throughout life, especially inmares (Goodwin, 2002). These bonds are mutually supportive and bonded pairs graze andrest together and engage in mutual grooming, affiliative neck overlapping and resting head-to-tail fly swishing (Goodwin, 1999 and 2002).The mare-foal bond begins to develop shortly after birth when the mare licks the foal for upto half an hour (Goodwin, 2002). Foals are able to stand and suckle within two hours of birthand stay very close to their dam’s side during the first weeks of life (

Ibid.

). Between one andtwo months of age, foals make exploratory trips away from their dam and engage in playwith other foals (

Ibid.

). Foals tend to associate preferentially with the foal of their dam’s mostpreferred associate (Weeks

et al

, 2000). From two to three months of age, foals begin tospend much of their time with other foals and form peer groups (Goodwin, 2002). Weaningtakes place at between eight and nine months of age (

Ibid.

).Horses are very playful animals. Play may involve running, frolicking, chasing, bucking, jumping, prancing, leaping, manipulation of an object, play fighting and play sexualbehaviour (McDonnell and Poulin, 2002). Solitary and object-directed play develop within thefirst month of life when foals remain close to their dam and social play develops from aroundone month of age as foals begin to interact with their peers and other members of the socialgroup (Goodwin, 2002). Play may be initiated by a nose-to-nose approach, nudging, nipping,tossing the head and pawing at the prospective play partner (McDonnell and Poulin, 2002).Play behaviour is vital to the development of the young horse, with up to 75% of the kineticactivity of foals devoted to play (Goodwin, 2002). Play continues to be an important activityeven in adulthood, especially for stallions (McDonnell and Poulin, 2002).

Perception and Communication

Vision

The retina of the horse contains a higher proportion of rods and a lower proportion of conescompared with the human retina. The higher proportion of rods means that horses’ vision isvery sensitive to light level and movement but is not optimal for colour vision and discerningdetail (Saslow, 2002). Horses have excellent vision in dim light and are able to make simplevisual discriminations and navigate around obstacles in conditions too dark for humans tosee (Hanggi and Inversoll, in press). Horses’ colour vision is not as good as that of humansbut research suggests that it is at least dichromatic (Smith and Goldman, 1999). The horses’visual acuity is around 20/30 on the Snellan scale, which is not as good as that of a human(20/20) but better than that of a dog (around 20/50) or a cat (20/75 to 20/100) (Timney andKeil, 1992).Compared with humans, horses possess a wider visual field because the eyes arepositioned to the sides of the head, which is advantageous for spotting predators butreduces the frontal overlapping binocular field of vision (Saslow, 2002). Horses have abinocular field in an arc of around 60

o

in front of the head, which enables depth perceptioncomparable with that of cats (Timney and Keil, 1999). Overall, as would be expected for aprey animal, horse vision appears to have evolved more for detection of predator approachfrom any angle than for accurate visual identification of stationary objects, especially thoseseen at a distance (Saslow, 2002).Horses are primarily visual communicators (Goodwin, 2002). Body postures and outlinesplay an important role in communication and co-ordination of the herd’s activities and horsesare extremely sensitive to subtle changes in the body language of their companions(Goodwin, 1999). The tense alarm posture alerts the herd to possible danger; a high

rounded body outline indicates excitement and a low straight outline indicates relaxation(Goodwin, 2002). Many parts of the body, including the tail, ears, face and legs, can be usedindependently or in combination to signal tension, excitement, arousal, fear, irritation,aggression, relaxation and pleasure (

Ibid.

)

Hearing

The range of hearing in the horse may not extend to frequencies quite as low as humanscan detect but it far exceeds the highest frequencies that can be heard by humans (over33000Hz in the horse compared to under 20000Hz in humans) (Saslow, 2002). The area ofbest sensitivity of hearing in the horse is broad and covers the range of the human voicebetter than a dog’s (

Ibid.

) The ears can be moved independently in the direction of thehorse’s attention (Goodwin, 2002).Horses also communicate vocally and the meaning of individual vocalisations may becomplex and context dependent (

Ibid.

). Vocal communication can serve to maintain contactover long distances, indicate excitement, deter contact in social interactions or initiateapproach between a mare and her foal (

Ibid.

).

Chemoreception

Smell and taste are linked neurologically in the horse, as they are in many other species(McGreevy, 2004). The olfactory structures are very large in the horse compared withhumans and it is likely that the horse’s capacity for chemoreception and reliance on chemicalinformation for identification are more similar to that of a dog (Saslow, 2002).Horses familiarise themselves with foreign objects by smelling them and odours areimportant for recognition of group members (McGreevy, 2004). Nose-to-nose sniffing is animportant part of greeting rituals between horses (

Ibid.

). Odours are used for communicationover time through marking behaviour, in courtship and in establishing the mare-foal bond(Goodwin, 2002).Taste is also important in the early bonding of the mare and foal (McGreevy, 2004). Tasteallows horses to discriminate between different foods and they can learn to avoid a food ifthey become ill within a short time of consuming it (Houpt

et al

, 1990).

Touch

Horses are very sensitive to tactile stimuli and react to pressures that are too light forhumans to feel (Saslow, 2002). Lansade

et al

(2008) found that most horses reacted topressure from a filament on the skin at the withers that was too small to be detected byhumans when applied to the index finger tip. This sensitivity is useful in detecting thepresence of biting flies landing on the skin, which initiates vigorous responses to dislodgethe insect, including skin rippling, tail swishing, ear flicking, head shaking, foot stomping andbiting at the area (Saslow, 2002).Touch is used for communication at close range: it promotes and maintains pair bondsduring mutual grooming and can be a form of social support in stressful situations, forexample, foals may press their body against their dam during novel or disturbing events(Goodwin, 2002).

Cognitive Abilities

Horses excel at simpler forms of learning such as classical and operant conditioning, whichis not surprising considering their trainability when these principles and practices are applied(Hanggi, 2005). Horses have also shown ease in stimulus generalisation and discriminationlearning and a number of recent studies have demonstrated their ability to solve advanced